In a conventional technology, a method for manufacturing a silicon single crystal wafer that is used as a semiconductor substrate material utilized in, e.g., various semiconductor devices generally includes a single-crystal growing process for manufacturing a single-crystal ingot by, e.g., a Czochralski (CZ) method or a floating zone (FZ) method and a wafer manufacturing (processing) process for slicing this single-crystal ingot and mirror-processing at least one main surface. A device is fabricated on the thus manufactured mirror-polished wafer.
Giving a further detailed explanation on the wafer manufacturing (processing) process, this process has a slicing step for slicing a single-crystal ingot to obtain thin discoid wafers, a chamfering step for chamfering an outer peripheral portion of each wafer to avoid cracks or chips of each wafer obtained at the slicing step, a lapping step for flattening this wafer, an etching step for removing a mechanical damage remaining in the chamfered and lapped wafer, a polishing step for finishing a wafer surface as a mirror surface, a cleaning step for cleaning the polished wafer to remove a polishing agent or a foreign matter that has adhered this wafer, and others. The main steps of the wafer processing process are described above, and steps such as a surface grinding step or a heat treatment step may be added, a certain step may be carried out on a plurality of stages, or the order of the steps may be changed.
In particular, the polishing step is divided into a primary polishing step that is called rough polishing and a final polishing step that is called precise polishing. Moreover, in some cases, the primary polishing step is further divided into two or more steps, and these steps are called, e.g., primary and secondary polishing steps. At each polishing step, a composition of a polishing slurry, a polishing pressure, and others are changed to provide conditions suitable for each step.
At the polishing step, for example, a polishing pad attached to an upper side of a rotatable turn table and an etched silicon single crystal wafer or the like supported on a wafer support plate of a polishing head are brought into contact with each other for polishing by using an appropriate pressure. At this time, an alkaline solution (which is called a polishing slurry or a polishing agent) containing a colloidal silica is used. When such a polishing agent is added to a contact surface of the polishing pad and the silicon single crystal wafer, the polishing slurry and the silicon single crystal wafer cause a mechanochemical effect, thereby advancing polishing.
Meanwhile, with advancement of miniaturization of a device rule, a size of a defect that can be a problem in device fabrication has been reduced. Further, small protrusive defects that are not acknowledged as a problem in the conventional technology have attracted attention. Furthermore, such defects are micro defects that are hardly detected by a conventional detector, but such micro defects can be observed by using, e.g., a confocal optical system laser microscope disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2004-193529. As micro detects, a single protrusion, a plurality of protrusions, a linear protrusion, a micro LPD (Light Point Defect) and others are confirmed.
There are also many such micro defects that are introduced at the polishing step. The defects introduced at the polishing step are generically referred to as PIDs (Polishing Induced Defects).
Furthermore, as explained above, generation of the micro PIDs that do not become a problem in the conventional technology have been needed to be prevented.
To suppress generation of the PID, for example, Japanese Unexamined Patent Publication (Kokai) No. 2005-45102 suggests using a predetermined polishing slurry. However, even if such a method is adopted, suppression of the PIDs is insufficient.